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Health Library

The Health Library at Vista Center is an affiliate of The Stanford Health Library.

The Health Library  is designed to help address the needs of individuals with vision loss, with comprehensive information about:

The library is staffed by visually impaired volunteers Health Library Volunteer conversing with clienttrained in researching health-related questions. Our volunteers are equipped to provide information, not medical advice. Although they are happy to help clients by researching  questions, we recommend that users contact their doctor or other health care professional when medical advice is needed.

 

The Health Library  produces three e-mail research lists:

These newsletters are compiled of research reports and excerpts from professional sources including Medline, Medscape, Nature and ophthalmology journals.

Individual health and medical information requests will be searched for and the results sent in large print or e-mail.   

Yearly updated packets of information are available about macular degeneration, glaucoma, diabetic retinopathy and others. Some are available in Spanish.  Our services are provided free to anyone in the blind and visually impaired community. E-mail or call the Health Library with your requests at 650-858-0202 Extension 132. thl@vistacenter.org 

How does the Eye Work (MS Word)

The Eye, a Verbal Description (MP3)

Braving the Low Vision Exam (MP3)

Nutrition and Eye Health (MS Word)

Medical News Articles

Artificial vision: what people with bionic eyes see

Visual prostheses, or "bionic eyes", promise to provide artificial vision to visually impaired people who could previously see. The devices consist of micro-electrodes surgically placed in or near one eye, along the optic nerve (which transmits impulses from the eye to the brain), or in the brain.  The micro-electrodes stimulate the parts of the visual system still functional in someone who has lost their sight. They do so by using tiny electrical pulses similar to those used in a bionic ear or cochlear implant. Electrical stimulation of the surviving neurons leads the person to perceive small spots of light called phosphenes. A phosphene is a phenomenon of experiencing seeing light without light actually entering the eye - like the colours you may see when you close your eyes.   These phosphenes in someone with a bionic eye can be used to map out the visual scene. So the vision provided by a bionic eye is not like natural sight. It is a series of flashing spots and shapes the person uses to interpret their environment through training - somewhat like a flashing mosaic. Currently, the vision provided by a bionic eye is very basic and can be used for tasks such as identifying the location of an object, detecting a person, or finding a doorway. Researchers hope future bionic eye devices will provide higher resolution vision, but this has inherent challenges.
(Read More)   How the bionic eye works - A bionic eye converts images from a video camera to a high-contrast representation of which a portion is selected for further  processing. An external video processor then converts this high-contrast image to electrical stimulation parameters, which are sent to electrodes implanted in the eye. The bionic eye recipient perceives a blurred image comprised of flashes of light. We know from the experience of our Melbourne patients that activity on the electrodes is seen as a series of bright flashes rather than as a steady erception. The world is thus flashing bursts of light arranged to represent the basic shape – like the height and width – and approximate location of an object in front of the camera. Other recipients have said this was like:  "looking at the night sky where you have  millions of twinkly lights that almost look like chaos." Recipients need to use these irregular flashes to interpret the camera image.The field of view (the extent of the observable world) is small – about 30 degrees wide or one hand span at arm's length – so recipients need to have a good memory to put the whole image together.  Improvements to the external camera  and video processing are able to assist here. For example, distance-sensing cameras can highlight obstacles such as a rubbish bin on the side walk, and thermal cameras can highlight human  shapes. Right now, the best outcomes rely heavily on patient engagement and ehabilitation.  The type of bionic eye that may be an option for patients is dependent on the cause of their vision loss. Retinal bionic eye implants are placed into the eyeball itself, and are only suitable for people who have lost their vision from specific diseases such as inherited types of retinal degeneration known as retinitis pigmentosa and age-related macular degeneration.  To date, only people with degenerative retinal diseases have been eligible to receive a bionic eye. Three retinal bionic eyes have been approved for commercial sale: the Argus II developed in the USA, the Alpha-AMS in Germany, and the IRIS V2 in France.  We ran clinical trial with 3 people, from 2012 -14, using a new  device developed in Australia. This device may have a safer surgical profile than  existing bionic eyes  as it is implanted at the back of the eye rather than inside the eye.  Prior to surgery, these patients  would not have been able to see a hand waving in front of their face. ith the bionic eye implant, they were able to locate objects on a table, and navigate around objects in their path while walking, demonstrating that the implant could provide useful visual information in the real world. We are preparing for a trial of a second-generation implant in the next year. These are all retinal implants and have mainly been used for  people with RP. Implants placed on either the optic nerve or directly into the brain may be able to provide benefit to people with a broader range of conditions, such as trauma or glaucoma. Devices for these particular conditions are still in the research phase but are expected to enter human clinical trials in the near future.  The quality of vision with a retinal implant heavily  depends on the residual eye health of the patient and the ability to interpret the created phosphenes. The implanted electrodes aim to replicate the function of missing light sensitive cells photo receptors). But there must be viable surviving neurons for the electrodes to interact with.  Another complicating factor is that there  are many neuron types in the retina but the electrodes are too large to selectively target individual types. For this reason, bionic eyes cannot replicate the sense of colour. In fact, artificial vision is very different from normal vision and takes a lot of getting used to. At present, there are several approaches to improve image quality. One is to increase the number of implanted micro-electrodes and make them smaller, allowing them to target selective neurons for more independent "pixels" and greater resolution. There are newer nanotechnology materials that might  allow the electrodes to be small enough to produce high-acuity resolution.  Another technique is to refine the electrical stimulation patterns to better focus the stimulation to activate smaller- sized clusters of neurons. We can also artificially increase resolution by  creating "virtual lectrodes" where electrical current is shared between two or more electrodes. These new stimulation methods could improve stability, reduce blurriness and possibly even provide rudimentary control over colour.   Ultimately, researchers are  seeking to understand and mimic the neural code the retina uses to communicate with the brain. If the firing patterns of photoreceptors could be replicated, the correct message would be transmitted to the brain. The  resulting vision would become significantly more natural. Combining these techniques, the level of  vision attainable might allow patients to independently navigate around without the use of a guide dog or cane. It could be possible to recognise everyday objects or even emotions on faces of loved ones. As to which approach is ultimately feasible, only time will tell.  One thing that is certain is bionic eyes will get better over time.  M Petoe, L  Ayton And M Shivdasani, The Conversation MedicalXpress 8/17/2017
2.%% From Diabetes Research Update: Treatment with Lucentis has been shown to reduce diabetic retinopathy  (DR)      by 2 steps or more at 1yr follow-up.  J Willis said that  Ranibizumab RX for DM eye disease not only improves visual acuity, but contributes to DR regression to a milder stage as well as potentially enhancing the visual function of patients with severe forms of DR.   Dr. Willis presented the findings of a cross-sectional study of Nat Health and Nutrition Exam Survey (NHANES) data on adults with nonproliferative diabetic retinopathy (NPDR) and PDR. The odds of patients having “significant visual function difficulty,” defined as moderate or greater difficulty with reading, visual-spatial tasks, mobility and driving, were greater in those with severe NPDR and PDR vs with no DR and mild/moderate DR. However, patients with severe NPDR/PDR treated with ranibizumab have been shown in prior studies to regress to mild/ mod NPDR, thus having potential for visual function improvement. Willis is an employee of Genentech, which provided funding for the study. Reference: Willis JR, et al. presented at: American Society of Retina Specialists meeting, Aug.2017; Healio 8/21/2017
 3.%% From Glaucoma Research Update: Adult Stem Cells (SC) and Glaucoma by Yvonne Ou MD UCSF    The field of adult stem cell research is very exciting, and particularly so for the eye. After all, the world’s first transplantation of cells that were derived from induced pluripotent stem cells (iPSCs) took place in the eye!. There are many different types of adult stem cells, including pluripotent stem cells. These SCs are special because they can mature and change into many different types of cells in the body, as well as replace themselves.  There are also several types of iPSCs, including human induced pluripotent stem cells. These stem cells are created from adult skin or blood cells that have been repro grammed back into a primitive state, which allows them to develop into any type of human cell needed for therapeutic purposes.  Although progress may seem slow to patients with vision loss who are awaiting a cure, this first transplantation actually took place only 10yrs after iPSCs were first discovered and made.  Although there is rigorous and scientifically sound work being done in adult stem cell labs all over the world, some SC cell “treatments” are not yet ready to treat glaucoma.  
Current Research - The term “stem cells to treat glaucoma” is broad and covers a wide variety of approaches. For example, in primary open-angle glaucoma (POAG) the drainage system does not properly drain the fluid inside the eye, and IOP can increase. One idea is to take iPSCs and use them to make the cells that drain fluid out of the eye (trabecular meshwork cells) in an effort to restore the eye’s drainage system.  Retinal Ganglion Cells (RGC): The method described above to fix the eye’s drainage system would not help a glaucoma patient who has already lost vision, since the vision loss is due to the death of the RGC that comprise the optic nerve. They connect the visual information processed by the retina, the “film” that lines the back of the eye, and the brain, where visual information is further processed. The RGC die in glaucoma, an irreversible process, which is why at present there is no cure for glaucoma.  Currently, the only RX we have is to lower eye pressure, a major risk factor for glaucoma. Thus, there is excitement around the possibility of using adult SCs to make RGCs and then to transplant these into the eye. This is an extremely challenging problem, however, since any transplanted stem cell-derived retinal ganglion cells, for example, would need to connect with their appropriate partners both in the retina and in the brain.  
(read more)  Scientists around the world are working to tackle this challenge, and we should continue to devote resources to it. In short, this partiulcar area of adult stem research is important, but not ready for patient care.  So, if you are a glaucoma patient with vision loss, where might you turn to find stem cell treatments?  You should talk to your ophthal mologist, which is a very important step. She/he should be up to date in the field, and may be aware of recent advances that even this article will not address, since the field is constantly changing and advancing. Buyer Beware.  Other patients might Google “stem cells” and “glaucoma.” Some patients may go to a clinical trial website thinking that any study listed on the website has a rubber stamp of approval from the federal government and is based on solid  cience. Unfortunately, this is not always the case.  Recent news stories have detailed how unsuspecting patients suffered severe vision damage after RX at certain illegitimate “trials.”  If you are considering a stem cell treatment for glaucoma, please think about the following very important factors: •In a typical clinical trial, patients are not asked to pay for the treatment. Indeed, for some clinical trials patients are reimbursed for costs associated with study visits, such as travel. Thus, be wary of RXs in which you are asked to pay for the procedure or the SCs. •A clinical trial or study in which the same stem cell “treatment” is used for many different diseases of the eye and/or that uses many different ways of delivering the stem cells is also concerning.  It suggests that there is not good understanding of how SC treatment works.  •Treatments that involve both eyes being treated at the same time are also a red flag.  •Finally, certain SC “clinics” have cropped up that offer unproven treatments, with websites prominently featuring patient testimonials. These clinics often use “autologous” stem cells, where the stem cells are harvested from the patient’s own fat (liposuction) or bone marrow. The (FDA) does not have as strict control over these types of SCs, so it is important to understand that these treatments have no regulatory protection. These clinics offer RXs that have not had any proper vetting for use in humans. For more information on clinical trials, view or download Clinical Trials: Your Questions Answered.  Summary  -- It is an exciting time for the adult stem cell field, as the pace of new discoveries and understanding about how SCs can be used for potential therapies is moving quickly. There are currently no FDA-approved stem cell RX for glaucoma.  Some glaucoma patients may feel, especially if they have very little vision left, that they have little to lose by paying for an unproven stem cell treatment. However, it is possible to lose all vision or even have worse outcomes such as loss of the eye or tumor growth.  Despite these cautions, we should continue investing our resources into legitimate research with adult stem cells, developing potential uses in the RX of eye disease. We just have to be patient and focus on treatments that have been carefully studied and tested. Bright Focus  edited for space thl; 5/23/2017

Stem cell secretions may protect against glaucoma

GLAUCOMA NIH 1/27/17: Stem cell secretions may protect against glaucoma - A new study in rats shows that stem cell secretions, called exosomes, appear to protect cells in the retina.  The findings point to potential therapies for glaucoma, a leading cause of blindness in the US. Exosomes are tiny membrane-enclosed packages that form inside of cells before getting expelled. Long thought of as part of a cellular disposal system, scientists have recently discovered that exosomes are packed with proteins, lipids and gene-regulating RNA. Studies have shown that exosomes from one cell can be taken up by another by fusing with the target cell’s membrane, spurring it to make new proteins. Ben Mead, PhD at NEI, and team investigated the role of stem cell exosomes on retinal ganglion cells (RGC) a type of retinal cell that forms the optic nerve that carries visual information from the eye to the brain. The death of RGCs leads to vision loss in glaucoma and other optic neuropathies. *
More...Stem cells have been the focus of therapeutic attempts to replace or repair tissues because of their ability to morph into any type of cell in the body. However, from a practical standpoint, using exosomes isolated from stem cells has some key advantages over transplanting whole stem cells. “Exosomes can be purified, stored and precisely dosed in ways that stem cells cannot,” Dr. M said.  Another important advantage is that exosomes  lack the risks associated with transplanting live stem cells into the eye, which can potentially lead to complications such as immune rejection and unwanted cell growth.  Mead used a rat glaucoma model to study the effects of exosomes isolated from bone marrow stem cells on RGCs.         Exosomes were injected weekly into the rats’ vitreous, the fluid within the center of the eye. Prior to injection, the exosomes were fluorescently labelled allowing the team to track the delivery of the exosome cargo into the RGCs. The exosome-treated rats lost about a third of their RGCs following optic nerve injury, versus a 90% loss among untreated rats. The treated RGCs also maintained function, according to electroretino-graphy, which measures electrical activity of retinal cells.  The team found that the protective effects of exosomes are regulated by microRNA, molecules that interfere with or silence gene expression. Further research is needed said S Tomarev, PhD coauthor.  We need to know which particular microRNA are involved and what proteins are being targeted upon arrival, he said  Finally, the most optimal exosome approach needs to be found. A lot will depend on how frequently exosomes need to be administered to achieve a therapeutic effect. Ref: Mead, B. and Tomarev S(2017)... Stem Cells Translational Medicine. NIH News 1/27/17